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POLYMERIC MATERIALS
AND SOFT CONDENSED MATTER
23.1 Polymerization Reactions for Synthetic
Polymers
23.2 Applications for Synthetic Polymers
23.3 Liquid Crystals
23.4 Natural Polymers
23CHAPTER
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Kevlar
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Multichip Module
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Crosslinking
in the exposed area
A material whose properties (e.g. solubility) can be changed by irradiation.
Photoresist (PR)
Deprotection
in the exposed area
Solubility: Enhanced Solubility: Decreased
Negative
Type PR
Positive
Type PR
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Organic Transistor, LEDs, Solar Cells and more
http://www.dupont.com/displays/
Printed electronic
calculator on a plastic
substrates
-Lightweight
-Flexible
-Low temperature processing
-Inexpensive
High Viewing Angle Flat-
Panel Displays
Organic Electronics
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Flexible and Transparent Display
https://news.samsung.com/kr/2019/07/25Samsung “Galaxy Fold”
LG Electronics, Transparent and Foldable Smartphone, US Patent 10,254,863
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Flexible and Transparent Display
https://news.samsung.com/uk/experts-predict-aquatic-
highways-air-taxis-and-space-hotels-for-life-in-50-years-time
PolyImides
Dupont Kapton film
Processing
Curing Ube Upilex film
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Polyethylene (UK)
PBD Rubber (Ger)
AN-BD Rubber (Ger)
Polyurethane (Ger)
St-BD Rubber (USA)
Polyisobutylene (USA)
1838,1839
Polymerization of
Vinyl Chloride & Styrene
(Vulcanization of Rubber)
Celluloid Rayon
Styrene-Diene Copolymers
& Phenolic Resin “Bakelite”(Lee Baekeland)
Urea-formaldehyde Resins
General Acceptance of the
Macromolecular Hypothesis
19301868 1893 1910 1920
Historical Overview of the Synthetic Polymers
19291890
Covalent Bonded
Macromolecular Structure(Herman Staudinger)
Nobel Prize in 1953
PMMAPS manufacture
Nylon 66 Manufacture
By DuPont
Conducting Polyacetylene(Shirakawa, MacDiarmid, Heeger)
Nobel Prize in 2000
1931 1936
PVAc
1937
Melamine-formaldehyde Resins
Neoprene Rubber
Polysulfide Rubber (Thiokol)
1939
1945 1960
Epoxy Resin
ABS, Polyesters, PC, PAN
Polysiloxane (Silicones)
Fluorocarbon Polymers
1980 1990 2015
X-Ray Diffraction (H. Mark)
NMR, FTIR LLS SPM
Polymerization Reaction(Wallace H. Carothers)
HDPE, LLDPE, PP(Karl Ziegler & Giulio Natta)
Nobel Prize in 1963
- Controlled Polymerization (Matyjaszewski, Grubbs)
- Dendrimers (Tomalia, Newkomb, Frechet)Anionic Living
Polym. (Szwarc)
Functional Polymers
Olefin Polym.
by Metallocene (Kaminski)
Tailor-Made
Polymers
High- Temperature
Polymers
Physical Chemistry of
Macromolecules(Paul J. Flory)
Nobel Prize in 1974
General Chemistry II
Hermann Staudinger: Father of Macromolecular Chemistry
(Nobel Prize, 1953)
In 1920, Hermann Staudinger, then professor of organic
chemistry at the Eigenössische Technische Hochschule
in Zurich, created a stir in the international chemical
community when he postulated that materials such as
natural rubber have very high molecular weights. In a
paper entitled "Ü ber Polymerisation," Staudinger
presented several reactions that form high molecular
weight molecules by linking together a large number of
small molecules. During this reaction, which he called
"polymerization," individual repeating units are joined
together by covalent bonds.
This new concept, referred to as "macromolecules" by
Staudinger in 1922, covered both synthetic and natural
polymers and was the key to a wide range of modern
polymeric materials and innovative applications. Today,
the molecular architectures of synthetic polymers and
biopolymers are tailored with high precision to meet the
demands of modern technology. The products of
polymer chemistry are diverse, from food packaging,
textile fibers, auto parts and toys, to membranes for
water desalination, carriers used in controlled drug
release and biopolymers for tissue engineering.
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Why are organic polymers (macromolecules) so useful?
Unique properties with high performance/cost ratio
lightweight, high toughness and modulus
excellent electrical properties
good durability in various environment
easy processing
versatile structure
Factors that govern physical properties of polymeric materials
- Chemical factors
Molecular structure
[Primary bond strength, Resonance stabilization, Crosslinking and branching
Molecular symmetry (structure regularity)]
Mechanism of bond cleavage
Secondary (hydrogen) bonding or van der Waals' bond forces
- Physical factors
Molecular weight and molecular weight distribution
Morphology
[Orientation, Crystallinity]
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The three states of matter
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Gas
Liquid
Solid
H2C CHnCH3
Polypropylene (PP)
H2C CH2n
Polyethylene (PE)
Hydrocarbons
Polymers
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Polymers (고분자): Poly = many, mer = part, Macromolecules (거대분자)
macromolecules built up by the linking together (polymerization) of large
numbers of smaller molecules (monomers)
Types of Polymers and Polymerizations
Composition or Structure (Carothers)
- Condensation
- Addition
Polymerization Reaction Mechanism (Flory)
- Step
- Chain
A polymer is classified as a condensation polymer,
if a) its synthesis involves the elimination of small molecules
or b) it contains functional groups as part of the polymer chain
or c) its repeating unit lacks certain atoms that are present in the
(hypothetical) monomer to which it can be degraded.
If a polymer does not fulfill any of these requirements, it is classified as an addition
polymer.
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Examples (Condensation Polymers)
b) polyurethanes
c) phenol-formaldehyde polymers
a) polyamides
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Chain Polymerization Step Polymerization
Only growth reaction adds repeating units one
at a time to the chain.
Monomer concentration decreases steadily throughout reaction.
High polymer is formed at once; polymer
molecular weight changes little throughout
reaction.
Long reaction times give high yields but affect molecular weight little.
Reaction mixture contains only monomer, high polymer, and about 10-8 part of growing chains.
Any two molecular species present can react.
Monomer disappears early in reaction : at DP* 10, less than 1% monomer remains.
Polymer molecular weight rises steadily throughout reaction.
Long reaction times are essential to obtain high molecular weights.
At any stage all molecular species are present in a calculable distribution.
Polymerization mechanism
Step and chain polymerizations differ in the length of time required for the complete growth of
full-sized polymer molecules
The two classifications, polymerization mechanism and polymer structure, cannot always be used interchangeably.
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Monomer
(AB or AA + BB Type)
A, B : Reactive
1 + 1 = 2
(monomer)
(dimer) 1 + 2 = 3
2 + 2 = 4
2 + 2 = 4
3 + 2 = 5
3 + 4 = 7
4 + 4 = 8
Step-growth Mechanism (Condensation Polymerization)
Monomer Reactive chain-end
Initiation >> PropagationInitiator
1 + 1 = 2, 2 + 1 = 3, 3 + 1 = 4, …, n + 1 = n+1
Reaction of monomer with Polymer end-groups
Chain-growth Mechanism (Addition Polymerization)
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◆ Addition polymerization 1 ~ free radical chain reaction
Ex. Polymerization of vinyl chloride, CH2=CHCl → Poly(vinyl chloride) (PVC)
Initiator ~ peroxide, R–O–O–R’
➢ Initiation:
➢ Propagation
23.1 POLYMERIZATION REACTIONS
FOR SYNTHETIC POLYMERS
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➢ Termination 2 (Disproportionation)
➢ Termination 1 (Coupling)
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❖ Branched polymeric chain
◆ Addition polymerization 2 ~ ion initiated chain reaction
❖ Polymerization of acrylonitrile
Initiator for this process: butyl lithium, (CH3CH2CH2CH2)–Li+ or Bu–Li+
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➢ Initiation
➢ Propagation
➢ Termination
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Chain Polymerization
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Monomer Reactive chain-end
Initiation >> PropagationInitiator
1 + 1 = 2, 2 + 1 = 3, 3 + 1 = 4, …, n + 1 = n+1
Reaction of monomer with Polymer end-groups
Chain-growth Mechanism (Addition Polymerization)
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◆ Condensation polymerization (A step polymerization)
→ A small molecule (e.g. H2O) is split off as each monomer unit is
attached to the growing polymer
Ex. Polymerization of 6-aminohexanoic acid → “Nylon 6”
Adipic acid + Hexamethylenediamine → “Nylon 66”
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Monomer
(AB or AA + BB Type)
A, B : Reactive
1 + 1 = 2
(monomer)
(dimer) 1 + 2 = 3
2 + 2 = 4
2 + 2 = 4
3 + 2 = 5
3 + 4 = 7
4 + 4 = 8
Step-growth Mechanism (Condensation Polymerization)
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Copolymers
~ Polymerization with two or more types of
monomers into irregular sequence along
the polymer chain
random – A and B randomly vary in chain
alternating – A and B alternate in polymer chain
block – large blocks of A alternate with large blocks of B
graft – chains of B grafted on to A backbone
A – B –
random
block
graft
alternating
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Cross-Linking: Nonlinear Synthetic Polymers
❖ With excess phenol, acid catalyst…
(1) Addition of formaldehyde to phenol to give methylolphenol
(2) Condensation reaction to form a linear polymer, novalac
◆ Phenol-formaldehyde copolymer ~ adhesives for plywood
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Fig. 23.3 A mixture of phenol / formaldehyde dissolved in acetic acid + HCl
→ Phenol-formaldehyde polymer
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❖With excess formaldehyde …
dimethylolphenol
trimethylolphenol
These monomers can form cross-linked polymers.
◆ “Bakelite” (1907), later became “Catalin”
Revolutionary non-flammable first artificial plastic made by Baekeland
Phenolic resin made from cross-linked phenol and formaldehyde
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dimethylolphenol
◆ “Bakelite” (1907), later became “Catalin”
Revolutionary non-flammable first artificial plastic made by Baekeland
Phenolic resin made from cross-linked phenol and formaldehyde
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Molecular Shape of Macromolecules
Linear
Branched
Block
Grafted
Crosslinked
Ladder
Star
Hyperbranched
Dendrimer
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Fibers
◆Cellulose
Glucose Cellulose
~ Made by chemical regeneration of the natural polymer cellulose,
a condensation polymer of glucose that is made by plants.
23.2 APPLICATIONS FOR SYNTHETIC
POLYMERS
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◆ Rayon ~ “semisynthetic” fiber
➢ Viscous rayon process
~ Digestion of cellulose with conc. NaOH:
–OH groups → –O–Na+ ionic groups
~ Reaction with CS2:
~ Ripening step:
Xanthate groups are removed to recover CS2
~ Addition of H2SO4:
Neutralize NaOH
Spin out (wet spinning) viscous rayon to form fibers
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Fig. 23.4 Filter paper (cellulose) will
dissolve in a concentrated ammonia
solution containing [Cu(NH3)4]2+ ions.
When the solution is extruded into
aqueous sulfuric acid, a dark blue
thread of rayon (regenerated cellulose)
precipitates.
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◆ Nylon
1930s Carothers (DuPont)
Condensation polymerization
to form amide linkage
Wallace H. Carothers(US,1896-1937)
35 ft. leg with a nylon stocking, L.A.
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➢ Condensation reaction:
➢ Repeating the above process gives “nylon 66”
• 66 → 6 carbon atoms on the starting diamine and
6 on the carboxylic acids
Adipic acid
Hexamethylenediamine
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Fig. 23.5
➢ Hexamethylenediamine
dissolved in water (lower layer)
➢ Adipyl chloride dissolved
in hexane (upper layer).
At the interface between the layers,
nylon forms and is drawn out onto
the stirring bar.
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◆ Polyester → Dicarboxylic acid + Dialcohol
Ex. Polyethylene terephthalate, “PET” “Dacron”
➢ Repeating the above process gives “Dacron”
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◆ Polyester → Dicarboxylic acid + Dialcohol
Ex. Polyethylene terephthalate, “PET” “Dacron”
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Plastics
~ Polymeric materials that can be molded or extruded into desired
shapes and that harden upon cooling or solvent evaporation
◆ Bakelite ~ first synthetic plastic, phenol-formaldehyde resin
◆Polyethylene
➢ Low-density polyethylene (LDPE) < 0.94 g cm–3
~ Free-radical-initiated addition polymerization of ethylene
monomer at high pressure (1000~3000 atm) and at 300~500oC
~ Free radicals frequently abstract hydrogen from the middle
of the chain
→ Resulting PE is not a perfect linear chain, heavily branched
→ Difficulty in packing of irregularly branched chains leads to LDPE
~ Soft, coating, trash bags, squeeze bottles
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➢ High-density polyethylene (HDPE)
~ 0.96 g cm–3
~ Linear PE synthesized with
Ziegler catalyst (1954) TiCl4 / Al(C2H5)3
~ Monomer added only to the coordination sphere of Ti4+
~ Hard, molding into bowls, toys
➢ Linear low density polyethylene (LLDPE)
~ Same metal-catalyzed reactions as HDPE
~ Deliberate copolymer with other 1-alkenes
~ Contains controlled short length of side groups
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HDPE
(high density polyethylene)
LDPE
(low density polyethylene)
Isotactic Polypropylene
Syndiotactic Polypropylene
LLDPE
(linear low density
polyethylene)
n
n
n
n
n
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H2C CH2n
H2C CHnCH3
Polyethylene (PE)
Polypropylene (PP)
HDPE Tm = 135 oC
Isotactic PP Tm = 165 oC
Syndiotactic PP Tm = 150 oC
Atactic PP Amorphous
Structure and Properties of Polyolefins
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◆ Polypropylene
~ Substitution of H in ethylene by a –CH3 group
~ Stiffer and harder than HDPE, higher m.p., endure high T
~ Medical instruments (sterilization at high temp)
❑ Different conformations of methyl groups
➢ Isotactic form
~ All methyl groups are arranged on the same side
~ Ziegler catalyst
➢ Syndiotactic form
~ Methyl groups are arranged alternately in a regular fashion
~ Natta catalyst (VCl4)
➢ Atatic form ~ random positioning of methyl groups
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Fig. 23.6 Structures of (a) isotactic, (b) syndiotactic, and (c) atactic polypropylene.
Nobel Prize Winner in Organic Chemistry
"for their
discoveries in the
field of the
chemistry and
technology of high
polymers“ (1963)
K. Ziegler G. Natta
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❖ Polymers with other elements beyond C and H
➢ Polyvinyl chloride (PVC)
➢ Polytetrafluoroethylene (Teflon)
~ Discovered by Plunkett at DuPont (1938)
~ Almost completely inert
~ Excellent heat stability (260oC)
~ Non-stick surface coating (frying pans)
( 2 2CF CF )n−
◆ Polystyrene
Roy J. Plunkett
(US, 1910-1994)
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Rubber
◆ Elastomer
~ Polymers that can be deformed to a great extent and still recover its original form
when the deforming stress is removed “Rubber” ~ term first used by Priestley
(rub with pencil eraser)
❖ Natural rubber
~ Polymer of isoprene (2-methylbutadiene), all cis-form, unsaturated
❑ Gutta percha ~ all trans-form of polyisoprene, tough (golf ball)
➢ Free-radical addition polymerization of isoprene
mixture of cis- and trans-forms, useless as an elastomer !
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H2C CHC CH2
CH3
From Rubber trees
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Fig. 23.8 In the polymerization of isoprene, a cis or trans configuration can form
at each double bond in the polymer. The blue arrows show the redistribution of
the electrons upon bond formation.
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Vulcanized Rubber
Changing the architecture of the natural rubber (linear polyisoprene) to a
crosslinked polymer dramatically changes the physical properties
– makes the material useful.
Crosslinked network
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❖ Vulcanization of rubber
~ Discovered by Goodyear (1839)
~ Addition of sulphur (< 5%)
to improve properties of natural rubber
Sulphur bridge between methyl groups
on different chains
❖ Synthetic rubbers
SBR rubber (Styrene-butadiene rubber)
NBR rubber (Acronitrile-butadiene rubber)
All-cis polybutadiene
~ Ziegler-Natta catalysts
Charles Goodyear(US, 1800-1860)
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◆ Electrically Conducting Polymers
➢ “Synthetic metals”
-conjugated chain of polymer backbone
Ground-state for the polymer chain → insulator
❖ Doping → conducting polymers
Partial oxidation or reduction of polymers
Electron donating dopants: Na, K, Li → n-type material
Electron accepting dopants: I2, PF6, BF4 → p-type material
➢ Polyacetylene doped with iodine
→ conductivity of ~ 5 x 104 S cm–1 (1/10 of Cu)
1 S(Siemens) = 1 A V–1 =1 mho = 1 [(ohm)]–1
Conducting Organic Polymers
(Nobel Prize in Chemistry 2000)
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trans-Polyacetylene Polythiophene
Poly(para-phenylene) Poly(para-pyridine)